The coordinated expression of a set of three genes will be studied in a mammalian cell linemutant K12. This temperature-sensitive cell cycle mutant isolated from the established cell line of Chinese hamster fibroblast, has the interesting property that the synthesis of three specific cellular proteins is greatly enhanced when the cells are incubated at the nonpermissive temperature. The general plan is to prepare cDNA clones which contain the mRNA sequences coding for these three proteins. Using these cDNA clones as probes, the kinetics of the induced transcription of these individual genes, as well as the routes by which their primary transcripts are processed, will be studied. Furthermore, these probes can be used to screen for cloned genomic sequences which contain this set of expressed genes, and to look for possible homologous sequence at their 5' termini, which may account for their coordinated expression. The question of gene rearrangemet which may have occurred during tissue culture growth will also be investigated. This same set of genes may also be expressed in chick fibroblast cells under glucose starvation conditions. The sequence organization of this set of genes in the chick genome can be compared to that of the hamster genome.